1. Technical Field
This invention relates to cellular phone communications and, more particularly, to an electronic device for blocking cellular phone communications.
2. Prior Art
The proliferation of portable cellular telephones has given rise to a new cultural phenomenon, visible and audible in many social settings, and public gathering places, institutions, and the like—ringing wireless telephones and open conversations. Depending on the locale and the type of setting, this phenomenon has become an intrusion at best, and at worst, it has become very annoying to others engaging in quiet discourse, or seeking peace.
Cellular communications are provided by mobile telephones in vehicles, or by personal cellular systems (PCS) and by multiple cell networks. Several different methods exist for establishing cellular communications, with differences in frequency range, modulation, signal processing, compression, bandwidth, demodulation and signal detection, etc.
The common denominator in all of these methods and techniques is based on predetermined control frequencies, to which the cellular units are directed or “listen” automatically, while they are in the standby mode. The control is two-way full duplex, such that there are a plurality of forward control channels (FCC) from the cell to the portable unit (uplink), and a plurality of reverse control channels (RCC) from the telephone to the cell (downlink). A maximum of three channels are assigned to each cell or sector. The cellular units automatically adjust to the best of these channels available in the cell or sector.
There are two possibilities in establishing a cellular conversation:
1) The subscriber initiates a conversation (origination)—the user initiates a conversation from the cellular unit to any telephone subscriber. In this case, he dials the destination subscriber number and presses the send button, and this begins a handshake routine opposite the local cellular cell, which provides service in a given area. The call handling is then passed to an area cellular mobile telephone switch office (MTSO), which checks the information, performs a verification that the subscriber is operating properly, and is entitled to receive service and then connects to the destination subscriber. This process is known as “call setup”.2) The subscriber receives a conversation (page)—the cellular system receives a request to establish a conversation with a cellular subscriber, and the area cellular MTSO performs a subscriber locate/search activity by sending a “search call” to all the cellular cells (connected to it) and these broadcast it on their control frequencies.
The destination subscribers (when in a standby mode) which are tuned to the local control frequency, respond to the search call and this begins a handshake routine with the area cellular MTSO. When finished, the system assigns a pair of specific frequencies, a forward control channel (FCC) from the cell to the portable unit, and a reverse control channel (RCC) from the telephone to the cell, in full duplex mode, to which the telephone and cell are tuned. Only after this, a ring command is broadcast to the telephone, activating the cellular subscriber's ringing unit, and this clears the way for a full conversation.
A basic condition in establishing any cellular conversation is that the control frequency and the service in a given area are received by the subscriber with a volume that provides a required signal-to-noise ratio (S/N) or better. Clearly, this condition is also true concerning the receiver equipment at the cellular cell, that is, that the information transmitted by the subscriber is received with the required S/N ratio, or better.
Therefore, there exists a need for a device that will prevent the ability to establish a cellular telephone conversation, either received or initiated, in a given area. Various reasons exist for this requirement, and these may be security-related, cultural, moral etc. For example, prevention of a cellular conversation on military bases is a classic security requirement. The same requirement exists in a theater, as a cultural norm in some countries.